Generally, broadcasting receiving apparatuses receive a broadcasting signal through an antenna and select a frequency band of a channel selected by a user to display a broadcasting program of the selected channel.
The broadcasting receiving apparatuses include an RF (Radio Frequency) receiving terminal receiving the broadcasting signal converted into an electrical signal using the antenna and a tuner selecting the frequency band of the channel selected by the user among different frequency bands transmitted from each of broadcasting stations.
A radio wave received at an RF receiving terminal has a very low power level due to an influence of attenuation and noise. Therefore, the RF receiving terminal requires a procedure of amplifying the received signal. However, when the received signal is amplified, a noise signal as well as a desired signal is amplified due to an external noise included in the received signal. What is therefore required is a function of minimizing the noise while amplifying the received signal.
In order to satisfy the function of minimizing the noise while amplifying the received signal at the RF receiving terminal, a Low Noise Amplifier (LNA) has been developed. The low noise amplifier is designed to have low noise figure by adjusting an operation point and a matching point.
Characteristics of a low noise ratio and a high amplification degree are required in the LNA.
The RF receiving terminal includes an RF attenuator for attenuating a signal amplified by the LNA to a signal having a predetermined level. The RF attenuator is included in an input terminal of the tuning unit. The RF attenuator attenuates an RF signal inputted according to a variable gain voltage of an automatic gain controller (ACC) producing a feedback control signal.
However, a path supplying a power to a line connected to the LNA is not provided in the RF attenuator. Therefore, the LNA is not effectively controlled. Thus, extension of a receive sensitivity range is impossible and stable receive sensitivity according to a received field strength (a weak electric field or a strong electric field) is not maintained.